There are many office chair designs which generally incorporate a tilt type control mechanism connecting the upper end of, for example, a conventional pedestal type base to the seat portion of the chair. This arrangement provides a substantially horizontal tilt axis which extends sideways across the seat portion directly adjacent the underside thereof, with the tilt axis generally disposed substantially directly over the pedestal and approximately midway between the front and rear edges of the seat. With this type of arrangement, rearward tilting of the seat portion results in the rear edge of the seat swinging downwardly and, simultaneously, the front edge of the seat swinging upwardly, thereby causing an undesirable lifting of the occupant's legs in the vicinity of the knees and thighs.
It is also known, of course, to provide flexing or tilting movement of the seat back portion of the chair relative to the seat portion by a hinged frame arrangement. However, such arrangements have not been completely satisfactory for lack of precise control of the flexing action of the seat back portion.
This invention provides a solution to both of the above mentioned problems by the unique arrangement of springs incorporated within the chair frame. Thus, in accordance with the present invention, the front edge of the seat portion flexes during the tilting of the seat portion of the chair, thus eliminating the aforementioned lifting of the pressure under the thighs. In addition, the seat back portion of the chair flexes independently of the seat tilt function of the pedestal base, thus delivering a correct amount of lumbar support in both the tilt and optional tilt lock modes.
In accordance with another feature of the invention, a continuous chair suspension system is provided wherein a steel seat/back frame is wrapped with a continuous suspension material, enveloped in urethane foam, and covered with upholstery, so that the occupant never "bottoms out" on a solid seat shell. The occupant thus remains cool from the continual exchange of air that flows through the seat suspension and padding. This eliminates the so-called "hot seat" syndrome commonly associated with solid shell chairs.
In accordance with one exemplary embodiment of the invention, therefore, a personal office or work chair is provided which includes an open frame construction wherein a seat portion of the chair includes a pair of front springs mounted on either side of the frame, each spring located between frame members extending rearwardly toward the chair seat back portion of the chair, and forwardly to the front edge of the seat portion. In a preferred arrangement, each spring comprises a strip of non-woven fiberglass epoxy resin material. These springs permit the forward portion of the seat frame, including a laterally extending forward frame member which connects the laterally spaced frame members, to flex downwardly upon rearward tilting of the seat portion of the chair. As a result, the tendency to lift the occupant's legs upwardly is lessened.
At the same time, the seat back portion of the chair includes an open frame wherein a pair of laterally spaced frame members are hingedly secured to the corresponding laterally spaced frame members of the seat portion by a hinge bar or rod extending across the frame. On each side of the frame, there is a relatively rigid but somewhat flexible plastic spring fixedly secured between adjacent seat frame and seat back frame members, overlapping the hinged connection between the seat and seat back frame portions. These relatively rigid plastic springs are generally L-shaped and are fixedly riveted to the seat frame members.
The pair of relatively rigid plastic springs are designed to provide controlled flexing of the seat back portion of the chair relative to the seat portion, as will be explained in greater detail further herein.
It is a further feature of the invention that rearward tilting of the seat back portion of the chair relative to the seat portion is limited by stop elements mounted on the hinge bar or rod and which are designed to engage a laterally extending, fixed bracing rod at the maximum tilt position.
In accordance with an exemplary embodiment of the invention therefore, there is provided a back spring adapted for connection between a seat frame portion and a seat back frame portion of a chair frame, the back spring comprising a relatively rigid but flexible member having a seat frame engaging portion and a seat back frame engaging portion, and an integral, arcuate hinge portion extending therebetween.
In another aspect of the invention, there is provided a front spring adapted for connection between a seat frame portion and a front lip portion of a chair frame, the front spring comprising a front lip engaging portion, and a seat frame engaging portion, wherein the front lip engaging portion and the seat engaging portion lie substantially in a single plane.
In another aspect, the invention provides a passive ergonomic chair comprising: an open frame construction including a seat back frame portion; a hinge connecting the seat frame portion to the seat back frame portion; a pair of rearward springs underlying respective end bushings of the hinge, each of the rearward springs comprising a relatively rigid curved member having a seat frame engaging portion and a seat back frame engaging portion, and an arcuate portion extending therebetween, the seat frame engaging portion being secured to the seat frame portion.
In still another aspect, the present invention provides an ergonomic chair wherein the seat frame portion includes: a forward lip portion extending across a forward end of the seat frame portion; and a pair of front springs adapted for connection between the seat portion and the forward lip portion of the frame, each of the front springs comprising a substantially straight forward lip engaging portion, and a substantially straight seat frame engaging portion, wherein the forward lip engaging portion and the seat engaging portion of each of the front springs lie substantially in a single plane.
In still another aspect, the present invention provides an ergonomic chair comprising: a substantially open frame construction including a seat frame portion and a seat back frame portion; a hinge connecting the seat frame portion to the seat back frame portion; a pair of rearward spring members underlying respective opposite end portions of the hinge, each of the springs comprising a relatively rigid member having a seat frame engaging portion and a seat back frame engaging portion, and an arcuate portion extending therebetween, the seat frame engaging portion fixed to the set frame portion; a forward lip portion extending across a forward end of the seat frame portion; a pair of front springs adapted for connection between the seat frame portion and the front lip portion of the chair frame, each of the front springs comprising a substantially straight forward lip engaging portion, and a substantially straight seat frame engaging portion; and means for limiting movement of the seat back frame portion relative to the seat frame portion.